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| United States Patent |
5,326,826
|
|
Roeschert
, et al.
|
July 5, 1994
|
Radiation-sensitive polymers containing diazocarbonyl groups and a
process for their preparation
Abstract
Radiation-sensitive polymers, a mixture containing these
radiation-sensitive polymers as binder, and a process for the preparation
of the radiation-sensitive polymer binders are disclosed. A positive
radiation-sensitive recording material containing the radiation-sensitive
polymer is also disclosed.
| Inventors:
|
Roeschert; Horst (Ober-Hilbersheim, DE);
Merrem; Hans-Joachim (Basking Ridge, NJ);
Pawlowski; Georg (Wiesbaden, DE);
Fuchs; Juergen (Floersheim/Wicker, DE);
Dammel; Ralph (Coventry, RI)
|
| Assignee:
|
Hoechst Aktiengesellschaft (Frankfurt am Main, DE)
|
| Appl. No.:
|
841532 |
| Filed:
|
February 26, 1992 |
Foreign Application Priority Data
| Current U.S. Class: |
525/326.5; 430/169; 430/170; 430/190; 430/192; 525/326.8; 525/328.8; 525/386; 526/262; 526/279; 526/309; 526/313 |
| Intern'l Class: |
C03F 007/023; C08F 030/08 |
| Field of Search: |
430/190,192,193,170,169
526/313,262,279,309
534/558,560,561
525/326.5,326.8,328.8,386
|
References Cited
U.S. Patent Documents
| 3779778 | Dec., 1973 | Smith et al.
| |
| 3837860 | Sep., 1974 | Roos.
| |
| 3902906 | Sep., 1975 | Iwama et al.
| |
| 4308368 | Dec., 1981 | Kubo et al. | 525/504.
|
| 4910123 | Mar., 1990 | Endo et al. | 430/326.
|
| 5087547 | Feb., 1992 | Taylor et al. | 430/190.
|
| Foreign Patent Documents |
| 242143 | Oct., 1987 | EP.
| |
| 307828 | Mar., 1989 | EP.
| |
| 0378067 | Jul., 1990 | EP.
| |
| 3028308 | Feb., 1982 | DE.
| |
| 3930087 | Mar., 1991 | DE.
| |
| 1494640 | Dec., 1977 | GB.
| |
Other References
G. Pawlowski et al., "A Novel Two Component Positive Photoresist for Deep
UV Lithography", Microelectronic Engineering 11(1990) Apr., Nos. 1/4,
Amsterdam, NL.
Patent Abstracts of Japan vol. 5, No. 88 (P-65) Jun. 9, 1981 & JP-A-56 035
129.
Patent Abstracts of Japan vol. 13, No. 347 (P-910)(3695) Aug. 4, 1989 &
JP-A-1 106 037.
C. G. Willson, "Organic Resist Materials--Theory and Chemistry",
Introduction to Microlithography Theory, Materials and Processing, ACS
Symposium Series 219, 87 (1983) pp. 88-159.
H. Sugiyama et al., "Positive Excimer Laser Resists Prepared with Aliphatic
Diazoketones", Proc. of the Ellenville Conf., (1988) pp. 51-61.
Y. Tani, et al., "A New Positive Resist for KrF Excimer Laser Lithography",
SPIE vol. 1086, Advances in Resist Technology and Processing VI, (1989)
pp. 22-32.
G. Schwarzkopf, "New 2-diazocyclohexane-1,3-dione Photoactive Compounds for
Deep U.V. Lithography", SPIE Advances in Resist Technology and Processing
V, vol. 920, (1988), pp. 51-58.
C. Willson et al., "New Diazoketone Dissolution Inhibitors for Deep U. V.
Photolithography", SPIE Advances in Resist Technology and Processing IV,
vol. 771, (1987), pp. 2-10.
J. Crivello, "Possibilities for Photoimaging Using Onium Salts", Polymer
Engineering and Science, Mid-Dec., vol. 23, No. 17, (1983), pp. 953-956.
F. Houlihan, et al., "An Evaluation of Nitrobenzyl Ester Chemistry for
Chemical Amplification Resists", SPIE, Advances in Resist Technology and
Processing V, vol. 920 (1988) pp. 67-74.
|
Primary Examiner: Bowers, Jr.; Charles L.
Assistant Examiner: Young; Christopher G.
Attorney, Agent or Firm: Foley & Lardner
Claims
What is claimed is:
1. A radiation-sensitive polymer, comprising:
(a) units having side groups of the general formula I
##STR8##
and (b) units having radiation-sensitive side groups of the general
formula II
##STR9##
wherein the numerical ratio of units (a) to units (b) is about 98:2 to
0:100, and
wherein
R is an acyclic, isocyclic or heterocyclic radical having 3 to 20 carbon
atoms,
X is a (C.sub.1 -C.sub.6)alkyl, (C.sub.1 -C.sub.6)alkoxy-(C.sub.1
-C.sub.6)alkyl, carboxyl, formyl, (C.sub.1 -C.sub.15)alkoxycarbonyl,
(C.sub.2 -C.sub.5)alkanoyl or (C.sub.1 -C.sub.6)alkoxy group or a halogen
atom,
m is 0, 1 or 2, it being possible for the radicals X to differ if m=2, and
n is 1 or 2, it being possible for the radicals R to differ if n=2.
2. The radiation-sensitive polymer as claimed in claim 1, wherein the
numerical ratio of the units containing groups of the general formula I to
those containing groups of the general formula II is from about 95:5 to
40:60.
3. The radiation-sensitive polymer as claimed in claim 1, wherein the
numerical ratio of the units containing groups of the general formula I to
those containing groups of the general formula II is from about 90:10 to
50:50.
4. The radiation-sensitive polymer as claimed in claim 1, which is derived
from a copolymer or terpolymer.
5. A polymer blend which comprises at least one radiation-sensitive polymer
as claimed in claim 1.
6. The radiation-sensitive polymer as claimed in claim 1, additionally
comprising units derived from monomers selected from the group consisting
of styrene, maleimide, vinyl alkyl ether and vinyltrialkylsilane.
7. The radiation-sensitive polymer as claimed in claim 1, wherein the
radical R is a straight-chain or branched alkyl radical having 3 to 10
carbon atoms, in which one or more CH.sub.2 groups are optionally replaced
by --O--, --NH-- or --CO--.
8. The radiation-sensitive polymer as claimed in claim 1, wherein the
radical R is a straight-chain or branched alkyl radical having 4 to 8
carbon atoms, in which one or more CH.sub.2 groups are optionally replaced
by --O--, --NH-- or --CO--.
9. The radiation-sensitive polymer as claimed in claim 1, wherein the
radical R is a cycloalkyl radical having 4 to 10 carbon atoms.
10. The radiation-sensitive polymer as claimed in claim 1, wherein the
radical R is a cycloalkyl radical having 4, 5 or 6 carbon atoms.
11. The radiation-sensitive polymer as claimed in claim 1, wherein the
radical R is an aralkyl radical having 1 to 11 carbon atoms in the
aliphatic part and 6 to 10 carbon atoms in the aromatic part, in which one
or more CH.sub.2 groups in the aliphatic part are optionally replaced by
--O--.
12. The radiation-sensitive polymer as claimed in claim 11, wherein the
radical R is an aralkyl radical having 2 to 5 carbon atoms in the
aliphatic part and 6 carbon atoms in the aromatic part.
13. The radiation-sensitive polymer as claimed in claim 1, wherein at least
one of the units (a) and (b) is derived from hydroxystyrene.
14. The radiation-sensitive polymer as claimed in claim 13, wherein the
hydroxystyrene is 4-hydroxystyrene.
15. The radiation-sensitive polymer as claimed in claim 13, wherein the
hydroxystyrene has one or two substituents on the aromatic ring, which
substituents are selected from the group consisting of methyl, ethyl,
propyl, methoxy and ethoxy.
16. The radiation-sensitive polymer as claimed in claim 13, wherein the
polymer has an average molecular weight of about 3,000 to 300,000.
17. The radiation-sensitive polymer as claimed in claim 13, wherein the
polymer has an average molecular weight of about 10,000 to 35,000.
18. The radiation-sensitive polymer as claimed in claim 1, wherein the
units (a) and (b) are derived from at least one monomer selected from the
group consisting of monohydroxyphenyl and dihydroxyphenyl methacrylate.
19. The radiation-sensitive polymer as claimed in claim 18, wherein the
monohydroxyphenyl or dihydroxyphenyl methacrylate has one or two
substituents X on the aromatic ring, which substituents are selected from
the group consisting of (C.sub.1 -C.sub.6)alkyl, (C.sub.1 -C.sub.6)alkoxy,
formyl and (C.sub.1 -C.sub.15)alkoxycarbonyl.
20. The radiation-sensitive polymer as claimed in claim 18, wherein the
polymer has an average molecular weight of about 1,000 to 100,000.
21. The radiation-sensitive polymer as claimed in claim 18, wherein the
polymer has an average molecular weight of about 2,000 to 50,000.
22. The radiation-sensitive polymer as claimed in claim 18, wherein the
polymer has an average molecular weight of about 3,000 to 30,000.
23. The radiation-sensitive polymer as claimed in claim 1, additionally
comprises units derived from a monomer selected from the group consisting
of styrene, optionally N-substituted maleimide, vinyl alkyl ethers and
vinyltrialkylsilane.
24. The radiation-sensitive polymer as claimed in claim 1, where X is a
(C.sub.1 -C.sub.6)alkyl, (C.sub.1 -C.sub.6)alkoxy-(C.sub.1 -C.sub.6)alkyl,
carboxyl, formyl, (C.sub.1 -C.sub.15)alkoxycarbonyl, (C.sub.2
-C.sub.5)alkanoyl or (C.sub.1 -C.sub.6)alkoxy group.
25. The radiation-sensitive polymer as claimed in claim 24, wherein m is 1
or 2.
26. The radiation-sensitive polymer as claimed in claim 24, wherein R is
tert-butyl, n-hexyl, nonyl, octadecyl, 2,5-dioxahexyl, cyclopentyl,
cyclohexyl, benzyl, phenethyl, phenoxymethyl or benzyloxymethyl.
27. The radiation-sensitive polymer as claimed in claim 24, wherein the
polymer has a low inherent absorption in the wavelength range from about
190 to 300 nm.
28. The radiation-sensitive polymer as claimed in claim 24, wherein the
numerical ratio of the units containing groups of the general formula I to
those containing groups of the general formula II is from about 95:5 to
40:60.
29. The radiation-sensitive polymer as claimed in claim 24, wherein the
numerical ratio of the units containing groups of the general formula I to
those containing groups of the general formula II is from about 90:10 to
50:50.
30. The radiation-sensitive polymer as claimed in claim 24, additionally
comprising units derived from monomers selected from the group consisting
of styrene, maleimide, vinyl alkyl ether and vinyltrialkylsilane.
31. The radiation-sensitive polymer as claimed in claim 24, wherein the
radical R is a straight-chain or branched alkyl radical having 4 to 8
carbon atoms, in which one or more CH.sub.2 groups are optionally replaced
by --O--, --NH-- or --CO--.
32. The radiation-sensitive polymer as claimed in claim 24, wherein the
radical R is a cycloalkyl radical having 4 to 10 carbon atoms.
33. The radiation-sensitive polymer as claimed in claim 24, wherein the
radical R is a cycloalkyl radical having 4, 5 or 6 carbon atoms.
34. The radiation-sensitive polymer as claimed in claim 24, wherein at
least one of the units (a) and (b) is derived from hydroxystyrene.
35. The radiation-sensitive polymer as claimed in claim 34, wherein the
hydroxystyrene has one or two substituents on the aromatic ring, which
substituents are selected from the group consisting of methyl, ethyl,
propyl, methoxy and ethoxy.
36. The radiation-sensitive polymer as claimed in claim 1, wherein X is
(C.sub.1 -C.sub.5)alkyl or (C.sub.1 -C.sub.5)alkoxy.
37. The radiation-sensitive polymer as claimed in claim 1, wherein m is 1
or 2.
38. The radiation-sensitive polymer as claimed in claim 37, wherein X is
methyl, ethyl or n-propyl.
39. The radiation-sensitive polymer as claimed in claim 38, wherein X is
methyl.
40. The radiation-sensitive polymer as claimed in claim 39, wherein m is 2.
41. The radiation-sensitive polymer as claimed in claim 1, wherein m is 1.
42. The radiation-sensitive polymer as claimed in claim 1, wherein m is 2.
43. The radiation-sensitive polymer as claimed in claim 1, wherein R is
tert-butyl, n-hexyl, nonyl, octadecyl, 2,5-dioxaheyl, cyclopentyl,
cyclohexyl, benzyl, phenethyl, phenoxymethyl or benzyloxymethyl.
44. The radiation-sensitive polymer as claimed in claim 1, wherein the
polymer has a low inherent absorption in the wavelength range from about
190 to 300 nm.
45. A process for the preparation of the radiation-sensitive polymer as
claimed in claim 1, comprising the steps of:
at least partially esterifying a polymer that contains phenolic hydroxyl
groups and that is not radiation-sensitive with a compound comprising
--CO--CH.sub.2 --CO--R groups, and then
treating the resultant product with a diazo transfer reagent.
46. The process as claimed in claim 45, wherein the diazo transfer reagent
is an alkanesulfonyl azide or benzenesulfonyl azide.
Description
BACKGROUND OF THE INVENTION
The present invention relates to radiation-sensitive polymers and to a
mixture containing these radiation-sensitive polymers as a binder. The
invention also relates to a process for the preparation of the
radiation-sensitive polymer binder and to a positive, radiation-sensitive
recording material prepared using the radiation-sensitive mixture. The
recording material is particularly suitable for the production of
photoresists, electronic components and printing plates and for chemical
milling.
Positive, radiation-sensitive mixtures have been known for a long time. The
use of these mixtures in radiation-sensitive copying materials, such as
blueprinting papers, planographic printing plates, colorproof sheets and
dry and liquid resists and for chemical milling has frequently been
described.
The continuing miniaturization of structures, for example, in chip
production, down to the range of less than 1 .mu.m, demands modified
lithographic techniques. In order to obtain an image of such fine
structures, short wavelength radiation is used, such as high-energy UV
light, electron beams and X-rays. The radiation-sensitive mixture must be
suited to the shortwave radiation. The demands which must be met by the
radiation-sensitive mixture are listed in the article by C. G. Willson
"Organic Resist Materials Theory and Chemistry" (Introduction to
Microlithography, Theory, Materials, and Processing, edited by L. F.
Thompson, C. G. Willson, M. J. Bowden, ACS Symp. Ser. 219: 87 (1983),
American Chemical Society, Washington). There is therefore an increased
demand for radiation-sensitive mixtures which can be used in the more
recent technologies, such as mid-UV or deep-UV lithography, with
illumination, for example, by means of Excimer lasers at wavelengths of
305 nm (XeF), 248 nm (KrF) and 193 nm (ArF), electron radiation
lithography and X-ray lithography. The mixtures are preferably also
sensitive in a broad spectral range and can thus be used in conventional
UV lithography.
Two routes have been taken in order to improve the resolution of
photoresists. On the one hand, an attempt was made to develop resists
based on conventional novolaks/.alpha.-diazocarbonyl compounds for the
deep-UV range, which resists have a further reduced solubility in the
non-irradiated regions. On the other hand, photoresist systems were
developed which are based on the principle of "chemical amplification."
In the presence of e-diazocarbonyl compounds, the solubility of novolaks in
alkali is greatly reduced, i.e., the .alpha.-diazocarbonyl compounds act
as solubility inhibitors. In addition to the diazonaphthoquinone sulfonic
acid esters, 2-diazo-1,3-dicarbonyl compounds, such as 5-diazo-Meldrum's
acid, derivatives of 2-diazocyclohexane-1,3-dione and
2-diazocyclopentane-1,3-dione and aliphatic 2-diazo-1,3-dicarbonyl
compounds are to be singled out. .alpha.-Phosphoryl-substituted
diazocarbonyl compounds and polyfunctional .alpha.-diazo-.beta.-ketoesters
are also described as photoactive inhibitors in positive resists,
especially those which are radiation-sensitive in the deep-UV range (DUV).
In their article "Positive Excimer Laser Resists Prepared with Aliphatic
Diazoketones" (Proc. of the Ellenville Conf. 51 (1988)), H. Sugiyama et
al. also propose .alpha.-diazoacetoacetates. Diazocarbonylsulfonyl
chlorides are described by Y. Tani et al. [SPIE Proc., Adv. in Resist
Techn. and Proc. 1086: 22 (1989)]. Further diazocarbonyl and
diazo-1,3-dicarbonyl compounds are given in G. Schwarzkopf [SPIE Proc.,
Adv. in Resist Techn. and Proc. 920: 51 (1988)]. are given in G.
Schwarzkopf (SPIE Proc., Adv. in Resist Techn. and Proc. 920: 51 (1988)).
Upon irradiation, all of these compounds rearrange to form ketene
derivatives. These ketene derivatives then react further with residual
moisture, which is frequently already present in the resist, to form
carboxylic acids. The carboxylic acids, in turn, increase the solubility
of the novolaks in aqueous-alkaline developers. However, it has been found
that some of the photoactive diazocarbonyl compounds bleed from the resist
layer under the relatively high processing temperatures frequently used in
practice and the radiation-sensitive mixture thus loses its original
activity, so that reproducible results are no longer possible.
It is true that photoactive components are known which have a lower
volatility, but these, depending on their structure, show a poorer
compatibility in the radiation-sensitive mixture. Especially when drying
the radiation-sensitive layers, this has a noticeable adverse effect due
to crystallization of the photoactive compound. In addition, these
components are frequently sparingly soluble in the conventional solvents.
Some of the diazocarbonyl compounds described additionally have the
disadvantage that the carbenes formed therefrom upon irradiation do not
have a stability in the matrix which is adequate for the desired
carboxylic acid formation. This leads to an inadequate difference in
solubility between the exposed and unexposed regions during development
and thus to an undesirably high degree of stripping in the unexposed
regions. An explanation for this phenomenon is proposed by C. G. Willson
et al. in SPIE Proc., Adv. in Resist Techn. and Proc. 771: 2 (1987).
.alpha.-Phosphoryl-substituted diazo compounds are not used for resists in
practice, since atoms which can be used as doping agents, such as the
phosphorus contained in these compounds, have to be strictly excluded in
the subsequent processing steps. It is true that derivatives of to image
differentiation are poor. Radiation-sensitive recording materials
containing the diazocarbonyl compounds described generally have an
inadequate photosensitivity, even in combination with highly transparent
binders.
Mixtures containing a binder which is insoluble in water and soluble or at
least swellable in aqueous-alkaline solutions, a component which forms a
strong acid under the action of actinic radiation, and a compound which
can be split by acid containing, for example, a C--O--C or C--O--Si bond,
are known in principle. See, e.g., DE 23 06 248 (=U.S. Pat. No.
3,779,778).
The compounds forming a strong acid on irradiation which have been used
are, in particular, onium salts, such as diazonium, phosphonium, sulfonium
and iodonium salts of non-nucleophilic acids, such as HSbF.sub.6,
HAsF.sub.6 or HPF.sub.6 (J. V. Crivello, Polym. Eng. Sci. 23: 953 (1983)).
In addition, halogen compounds, particularly trichloromethyltriazine
derivatives or trichloromethyloxadiazole derivatives,
o-quinonediazidesulfonyl chlorides, o-quinonediazide-4-sulfonic acid
esters, organometallic/organohalogen combinations,
bis(sulfonyl)diazomethanes, sulfonylcarbonyldiazomethanes (DE 39 30 087)
and nitrobenzyltosylates (F. M. Houlihan et al., SPIE Proc., Adv. in
Resist Techn. and Proc. 920:67 (1988)) have been recommended.
The strong acid formed upon irradiation of the materials described above
splits the C--O--C or C--O--Si bonds of the acid-labile compounds. As a
result, the exposed regions of the photosensitive layers become more
soluble in an aqueous-alkaline developer. If shortwave radiation is used
for irradiation, this demands new binders which are highly transparent at
these wavelengths. However, radiation-sensitive layers composed of
mixtures comprising such a highly transparent, radiation-insensitive
binder, an acid-labile compound having at least one C--O--C or C--O--Si
bond which can be split by acid, and a compound which forms a strong acid
on irradiation have a solubility in the developer in the non-irradiated
regions that is too high. This is reflected in an unacceptable
dark-erosion. The consequence of this is an inadequate edge profile and a
reduced resolution. Overall, the systems described above based on the
principle of "chemical amplification" do have an exceptionally high
photosensitivity (50 mJ/cm.sup.2 and less), but an unsatisfactory
resolution for structures in the range of less than 0.5 .mu.m.
Radiation-sensitive mixtures, which contain radiation-sensitive polymers,
have already been described for a number of applications. Condensation
products of novolak resins with orthoquinonediazide compounds (see, e.g.,
DE 30 09 873=U.S. Pat. No. 4,308,368, DE 30 28 308, EP 242,143) are
particularly important. However, as a result of the novolak constituent,
these radiation-sensitive polymers have absorption characteristics which
make them unsuitable for exposure in the DUV range.
More transparent, radiation-sensitive polymers can be prepared by a
condensation reaction of hydroxyl group-containing polymers, such as
poly(4-hydroxystyrene) or copolymers of pyrogallol with ketones, and
polyacrylates with 2,1-diazonaphthoquinone-5- and/or -4-sulfonic acid
chlorides. The hydroxyl group-containing polymers have, however, an
extremely high solubility in standard developers, which is reduced only
after the predominant proportion of the free hydroxyl groups has reacted.
This results in a high proportion of diazonaphthoquinone units. This leads
to unacceptable optical characteristics especially at 248 nm. Examples of
mixtures containing such polymers are given in DE 20 28 903 (=U.S. Pat.
No. 3,837,860), DE 23 52 139, DE 24 61 912 (=GB 1,494,640) and EP 307,828.
Radiation-sensitive polymers having a diazocarbonyl group as a
photosensitive component are given in JP 01-106,037. The
radiation-sensitive unit is bonded to the alkyl chain of a
4-alkyl-substituted polystyrene. The polymers are characterized by low
thermal stability and an inadequate sensitivity to radiation.
2-Diazo-1,3-dicarbonyl units, bonded to conventional novolak resins, have,
as already discussed in detail above, a low transparency in the range of
shortwave radiation and unsatisfactory bleed characteristics.
Radiation-sensitive recording materials containing polymers having
2-diazo-1,3-dicarbonyl groups as a radiation-sensitive structural element,
in particular those containing maleimide/olefin copolymers, are disclosed
in U.S. Pat. No. 4,910,123. The resist materials prepared with these
polymers have, however, a radiation sensitivity of only about 50
mJ/cm.sup.2.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a
radiation-sensitive mixture having high photosensitivity in the DUV
region.
It is a further object of the invention to provide a mixture which does not
have the disadvantages described above for the numerous known mixtures.
It is yet another object of the invention to provide a radiation-sensitive
layer displaying a good differentiation between the exposed and unexposed
regions of the layer.
It is another object of the invention to provide a radiation-sensitive
mixture that is readily compatible under the diverse process conditions
used in practice and that has a high thermal stability, so that resolution
in the sub-half-micrometer range is possible with an acceptable resist
profile.
These and other objects according to the invention are provided by a
radiation-sensitive polymer which is insoluble in water and soluble or at
least swellable in aqueous-alkaline solutions. The polymer comprises:
(a) units having side groups of the formula I
##STR1##
and
(b) units having radiation-sensitive side groups of the general formula II
##STR2##
wherein the numerical ratio of units (a) to units (b) is about 98:2 to
0:100, where
R is an acyclic, isocyclic or heterocyclic radical having 3 to 20 carbon
atoms,
X is a (C.sub.1 -C.sub.6)alkyl, (C.sub.1 -C.sub.6)alkoxy-(C.sub.1
-C.sub.6)alkyl, carboxyl, formyl, (C.sub.1 -C.sub.15)alkoxycarbonyl,
(C.sub.2 -C.sub.5)alkanoyl or (C.sub.1 -C.sub.6)alkoxy group or a halogen
atom,
m is 0, 1 or 2, it being possible for the radicals X to differ if m=2, and
n is 1 or 2, it being possible for the radicals R to differ if n=2.
Also provided according to the present invention is a positive,
radiation-sensitive mixture, comprising (a) a compound containing at least
one C--O--C or C--O--Si bond which can be split by acid, (b) a compound
which forms a strong acid on irradiation, and (c) a binder which is
insoluble in water and soluble or at least swellable in aqueous-alkaline
solutions, comprising a radiation-sensitive polymer according to the
invention. A process for the preparation of radiation-sensitive polymers
according to the invention is also provided, comprising the steps of at
least partly esterifying a polymer that contains phenolic hydroxyl groups
and that is not radiation-sensitive with a compound comprising
--CO--CH.sub.2 --CO--R groups, and then treating the resultant product
with a diazo transfer reagent.
A positive, radiation-sensitive recording material according to the present
invention comprises a support material, and a radiation-sensitive layer
comprising a radiation-sensitive polymer or mixture according to the
invention coated on the support material.
A method of producing an image according to the invention comprises the
steps of imagewise irradiating a positive, radiation-sensitive recording
material according to the invention with radiation having a wavelength of
about 190 to 400 nm, and developing the recording material to produce a
positive image.
Other objects, features and advantages of the present invention will become
apparent from the following detailed description. It should be understood,
however, that the detailed description and the specific examples, while
indicating preferred embodiments of the invention, are given by way of
illustration only, since various changes and modifications within the
spirit and scope of the invention will become apparent to those skilled in
the art from this detailed description.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A radiation-sensitive polymer according to the present invention comprises
(a) units having side groups of the general formula I
##STR3##
and, derived therefrom,
(b) units having radiation-sensitive side groups of the general formula II
##STR4##
wherein a numerical ratio of units (a) to units (b) is about 98:2 to
0:100, and where
R is an acyclic, isocyclic or heterocyclic radical having 3 to 20 carbon
atoms,
X is a (C.sub.1 -C.sub.6)alkyl, (C.sub.1 -C.sub.6)alkoxy-(C.sub.1
-C.sub.6)alkyl, carboxyl, formyl, (C.sub.1 -C.sub.15)alkoxycarbonyl,
(C.sub.2 -C.sub.5)alkanoyl or (C.sub.1 -C.sub.6)alkoxy or a halogen atom,
m is 0, 1 or 2, it being possible for the radicals X to differ if m=2, and
n is 1 or 2, it being possible for the radicals R to differ if n=2.
In addition to the units containing a group of the general formula I or II,
the radiation-sensitive polymers can also contain other units. The
solubility and the transparency (in the desired wavelength range) can be
adjusted in a desired manner by the incorporation of such additional units
in the radiation-sensitive polymer. The radical R can optionally be
substituted, in particular by (C.sub.1 -C.sub.3)alkyl, (C.sub.1
-C.sub.3)alkoxy, halogen, amino or nitro. If the radical R is substituted,
the substitution is preferably by (C.sub.1 -C.sub.3)alkyl or (C.sub.1
-C.sub.3)alkoxy. However, if R is an alkyl radical, the latter is
preferably unsubstituted.
Particularly suitable radicals R are acyclic, C-containing radicals,
especially alkyl radicals. These can be straight-chain or branched and
contain preferably 3 to 10 and in particular 4 to 8 chain members. Pure
carbon chains are particularly preferred, but alkyl radicals in which
CH.sub.2 groups have been replaced by oxygen atoms or --NH-- and/or
carbonyl groups are also suitable. The alkyl radicals R can thus contain
--CO--O--, --CO--NH-- and/or --O--CO--NH-- groups. In addition, --CH--
groups can be replaced by --N--. Preferred alkyl radicals R in which
--CH.sub.2 -- groups have been replaced by --O-- bridges are those which
contain two of these --O-- bridges. If the chains are pure, in particular
straight-chain, carbon chains, it is not essential to restrict the number
of carbons; alkyl radicals containing up to 20 carbon atoms are suitable.
However, the tert-butyl radical is particularly preferred.
If R is a cycloalkyl radical, which is to be understood as including
bicycloalkyl and polycycloalkyl radicals, the number of ring carbons is
preferably 4, 5, 6 or 10, particularly preferably 4, 5 or 6. The
unsubstituted representatives are particularly preferred. Examples which
may be mentioned are the cyclobutyl radical, the cyclopentyl radical and
the cyclohexyl radical. However, the cyclohexyl radical is particularly
preferred.
The radical R can also be an aralkyl radical or, in the broader sense, a
radical to which the aromatic part is bonded via a non-aromatic,
C-containing bridge member. If R is an aralkyl radical, the number of
members in the aliphatic part is preferably 1 to 11, particularly
preferably 2 to 5. Of the purely aliphatic bridge members, methylene or
ethane-1,2-diyl is preferred. If a CH.sub.2 group in the ethane-1,2-diyl
bridge is replaced by an oxygen atom, this preferably forms the bridge
between the aromatic and the aliphatic part of the radical R. In a
three-membered bridge containing two carbon chain members and one oxygen
chain member, the oxygen is preferably arranged between the two CH.sub.2
groups. Radicals to be mentioned in particular are the benzyl radical and
the phenethyl radical for the first case, the phenoxymethyl radical for
the second case and the benzyloxymethyl radical for the third case. In
this context, however, those radicals in which CH.sub.2 groups in the
aliphatic part have been replaced not only by --O-- but also by --NH
and/or -- CO--, and in which --CH-- has been replaced by --N--, should
also be regarded as aralkyl radicals. Examples of such radicals are
phenoxycarbonyl and benzyloxycarbonyl radicals, and also
benzyloxy-carbonylamino and phenoxycarbonylamino radicals. The radical R
can, however, also be a phthalimido group. The general criterion is that
the bridge member contain at least one carbon atom in the chain in
addition to any heteroatoms which may be present. The aromatic part of the
araliphatic radical preferably consists of 6 to 10, and particularly
preferably of 6, carbon atoms. If this part is directly adjacent to a
carbonyl group, i.e., an aroyl radical is present, the aliphatic part can
contain an arbitrary number of carbon atoms.
The aromatic radicals R are preferably isocyclic, i.e., they do not contain
any heteroatoms, such as, for example, oxygen, in their ring system. The
aromatic radical contains in particular 6 to 10 carbon atoms, preferably 6
carbon atoms, i.e., it is a phenyl radical. However, aromatic radicals R
are not preferred.
Of all of the above-mentioned radicals R, tert-butyl, n-hexyl, nonyl,
octadecyl, 2,5-dioxahexyl, cyclopentyl, cyclohexyl, benzyl, phenethyl,
phenoxymethyl and benzyloxymethyl are preferred. The tert-butyl radical,
the phenethyl radical, the phenoxymethyl radical and the cyclohexyl
radical are particularly preferred.
The radiation-sensitive polymer on which the radiation-sensitive polymer
binder is based contains groups of the general formula I. Suitable
polymers containing such mono- or dihydroxyphenyl groups are, for example,
transparent novolaks and homopolymers from the class comprising
poly(hydroxy)styrenes, monosubstituted (m=1) and disubstituted (m=2)
poly(hydroxy)styrenes, substituted and unsubstituted
poly(.alpha.-methylhydroxystyrenes) and monoesters of acrylic acid and
methacrylic acid with aromatic compounds containing substituted or
unsubstituted phenolic groups (for example, di- or trihydroxybenzenes and
their derivatives). However, copolymers and terpolymers of monomers
containing groups of the general formula I can also be used. Finally,
copolymers and terpolymers of such monomers and others which contain no
optionally substituted (di)hydroxyphenyl groups are also suitable.
Suitable comonomers and termonomers are, for example, styrene, maleimide,
N-substituted maleimides, vinyl alkyl ethers and vinyltrialkylsilanes. The
proportion of such "other" monomers in the polymer can differ
substantially. Thus, the proportion of styrene in a styrene/hydroxystyrene
copolymer can be, for example, up to about 85% by weight. Homopolymers,
copolymers and terpolymers are always preferred to mixtures (blends).
The radiation-sensitive binders according to the invention prepared from
these polymers are distinguished in particular by the fact that they
readily dissolve the other constituents of the radiation-sensitive mixture
according to the invention and have a low inherent absorption, i.e., a
high transparency, particularly in the wavelength range from about 190 to
300 nm, and bleach severely on exposure to actinic radiation. These
conditions are not met by known binders based on conventional novolaks.
However, novolaks can also be used in the mixtures according to the
invention if they are mixed with other binders of higher transparency,
which are described in more detail below. The mixing ratio depends on the
structure of the highly transparent binder, which determines not only the
degree of inherent absorption in the specified wavelength range, but also
the miscibility with the other constituents of the radiation-sensitive
mixture. The binder mixture can generally contain up to about 40% by
weight, preferably up to about 25% by weight, of a novolak. Upon
irradiation with light having a wavelength of 248 nm, suitable novolaks or
novolak mixtures, in a layer about 1.0 .mu.m thick, have an absorption of
less than about 0.5; their average molecular weight is between about 500
and 30,000.
Among the unsubstituted poly(hydroxy)styrenes (PHS), the copolymers of
4-hydroxystyrene are preferred and among the substituted PHS the
homopolymers and copolymers of 3-alkyl- and 3,5-dialky-4-hydroxystyrene
are preferred. The average molecular weight is between about 3,000 and
300,000, but preferably between about 5,000 and 100,000, particularly
preferably between about 10,000 and 35,000.
In the case of the monosubstituted poly(4-hydroxy)-styrenes, the
substituents X are preferably (C.sub.1 -C.sub.5)alkyl and (C.sub.1
-C.sub.5)alkoxy groups. Particularly suitable alkyl groups are methyl,
ethyl and n-propyl groups. Radicals X having a lower number of carbon
atoms are preferred. The methyl group is particularly preferred. The
number m of substituents X is 0, 1 or 2, preferably 1. If m is 2, X is
preferably methyl.
In the case of poly(.alpha.-methyl-4-hydroxy)styrenes, the same applies as
in the case of the polymers without an .alpha.-methyl group. However,
these are not preferred.
Suitable monomers which may be mentioned for the preparation of
poly(methacrylic acid) mono- and dihydroxyphenyl esters are the
monomethacrylates of di- and trihydroxybenzenes, in particular of
pyrocatechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol and
hydroxyhydroquinone and the monomethacrylates of various substituted
trihydroxybenzaldehydes and trihydroxybenzoic acid esters. Particularly
suitable substituents X are (C.sub.1 -C.sub.6)alkyl, (C.sub.1
-C.sub.6)alkoxy, formyl and (C.sub.1 -C.sub.15)alkoxycarbonyl groups.
Examples which may be mentioned are gallaldehyde (X=CHO), various gallic
acid esters [X=COOR'; R'=(C.sub.1 -C.sub.15)alkyl] and also the monoesters
of trihydroxybenzenes with other substitution patterns. All of these
monomers can optionally be further substituted. With regard to the
substituents on the aromatic ring and also with regard to the alcohol
component OR' of the gallic acid esters there are no restrictions other
than that, under the reaction conditions, the functional group must not
react in an undesired manner, in particular there must be no
transesterification or ester splitting. Trihydroxy-substituted
benzaldehydes and alkyl gallates are therefore particularly preferred.
Particularly preferred alkyl radicals are methyl, propyl, octyl and
dodecyl radicals. In these cases m is preferably 1. The average molecular
weight of these polymers is between about 1,000 and 100,000, preferably
between about 2,000 and 50,000 and particularly preferably between about
3,000 and 30,000.
Preferred monomers for poly(methacrylic acid esters) are the
monomethacrylates of pyrocatechol, hydroquinone, phloroglucinol and
hydroxyhydroquinone. The 2-, 3- and 4-hydroxyphenyl esters and the
3,5-dihydroxyphenyl esters of methacrylic acid are particularly preferred.
The structure of some of the polymer units having side groups of the
general formula I which preferably occur in the polymers according to the
invention is indicated below:
##STR5##
Suitable copolymers and terpolymers containing groups of the general
formula I contain, for example, units of 4-hydroxystyrene and/or one or
two of the following monomers: 3,5-dialkyl-4-hydroxysytrene,
3-alkyl-4-hydroxystyrene, 3-hydroxystyrene, vinyl (C.sub.1 -C.sub.25)
alkyl ethers, styrene, methyl methacrylate and methyl acrylate.
Particularly preferred vinyl alkyl ethers are those having a medium-length
chain or longer-length chain alkyl radical, such as n-hexyl, n-octyl,
n-dodecyl and n-octadecyl. The average molecular weight of the various
copolymers and terpolymers is between about 3,000 and 300,000, preferably
between about 5,000 and 100,000 and particularly preferably between about
5,000 and 35,000.
Mixtures having increased stability towards oxygen plasma are obtained if
silicon-containing vinyl monomers, for example, vinyltrimethylsilane, are
used to prepare the copolymers or terpolymers. The transparency of these
binders is generally even higher in the DUV range, so that an improved
imaging is possible.
Copolymers of the various hydroxystyrenes with N-substituted maleimides can
also be used with equal success. The substituents on the nitrogen atom of
the maleimide are aliphatic, cycloaliphatic, araliphatic and also aromatic
radicals. These may be either substituted or unsubstituted. Particularly
preferred N-substituents are the phenyl radical and the cycloalkyl
radical.
Poly(methacrylic acid monoesters) are preferably used as homopolymers or as
copolymers or terpolymers with maleimide and/or styrene. In principle,
virtually all polymers can be used which contain phenolic hydroxyl groups
and no further groups reacting with carboxylic acid esters, or which,
under the reaction conditions described, react with clear ester formation.
Overall, the following may be mentioned as particularly preferred binders
containing groups of the general formula I: poly (3-methyl-4-hydroxy)
styrene, copolymers of 3-methyl-4-hydroxystyrene and 4-hydroxystyrene,
copolymers of 3,5-dimethyl-4-hydroxystyrene and 4-hydroxystyrene, and also
copolymers of 4-hydroxystyrene and styrene. Mixtures (blends) of these and
other polymers are also suitable.
The amount of binder in the radiation-sensitive mixture is generally about
40 to 100% by weight, in particular about 50 to 95% by weight and
preferably about 60 to 90% by weight, based on the total weight of solid
contained therein. It is clear from this that in the extreme case a
radiation-sensitive polymer on its own, without the addition of an
acid-cleavable compound containing a C--O--C or C--O--Si bond and a
compound forming a strong acid on irradiation, is also suitable. However,
such an embodiment is not preferred.
The ratio of the polymer units containing groups of the general formula I
to those containing groups of the general formula II varies between about
98:2 and 0:100, preferably between about 95:5 and 40:60 and particularly
preferably between about 90:10 and 50:50. The optimum ratio is dependent
primarily on the structure of the binder and thus on the solubility of the
resulting formulation and on the transparency of the layer in the DUV
region, especially at a wavelength of 248 nm.
The following classes of compound in particular have proved suitable as
acid-cleavable materials in the radiation-sensitive mixture according to
the invention:
(a) those containing at least one orthocarboxlic acid ester and/or
carboxylic acid amidoacetal group, the compounds also having a polymer
character and it being possible for the said groups to occur in the main
chain or a side chain,
(b) oligomer or polymer compounds containing recurring acetal and/or ketal
groups in the main chain,
(c) compounds containing at least one enol ether or N-acryliminocarbonate
group,
(d) cyclic acetals or ketals of .beta.-ketoesters or .beta.-ketoamides,
(e) compounds containing silyl ether groups,
(f) compounds containing silyl enol ether groups,
(g) monoacetals or monoketals of aldehydes or ketones, the solubility of
which in the developer is between 0.1 and 100 g/l,
(h) ethers based on tertiary alcohols, and
(i) carboxylic acid esters and carbonates, the alcohol component of which
is a tertiary alcohol, an allyl alcohol or a benzyl alcohol.
Acid-cleavable compounds have already been described briefly further above.
Thus, acid-cleavable compounds of type (a) as components of
radiation-sensitive mixtures are described in detail in DE 26 10 842 and
DE 29 28 636. Mixtures containing compounds of type (b) are described in
DE 23 06 248 and DE 27 18 254. Compounds of type (c) are described in EP
6,626 and EP 6,627. Compounds of type (d) are proposed in EP 202,196 and
compounds which are to be regarded as being of type (e) are proposed in DE
35 44 165 and DE 36 01 264. Compounds of type (f) are found in DE 37 30
785 and DE 37 30 783, while compounds of the (g) are discussed in DE 37 30
787. Compounds of type (h) are described, for example, in U.S. Pat. No.
4,603,101 and compounds of type (i), for example, in U.S. Pat. No.
4,491,628 and by J. M. Frechet et al., J. Imaging Sci. 30: 59-64 (1986).
Mixtures of the above-mentioned acid-cleavable materials can also be
employed. However, use of an acid-cleavable material which belongs to only
one of the above-mentioned categories is preferred, especially a material
having at least one C--O--C bond splittable by acid, i.e., those materials
which belong to the types (a), (b), (g) and (i) are particularly
preferred. Under type (b) the polymeric acetals are preferred; among the
acid-cleavable materials of type (g) those compounds are preferred that
are derived from aldehydes or ketones having a boiling point above about
150.degree. C., preferably above about 200.degree. C.
The content of acid-cleavable material in the radiation-sensitive mixture
according to the invention should be about 1 to 50% by weight, preferably
about 10 to 40% by weight, in each case based on the total weight of the
layer.
Compounds suitable for the mixture according to the invention which
liberate a strong acid under the action of actinic radiation have already
been described in detail above. The use of specific photolytic
acid-forming agents, such as onium salts, halogen compounds and
nitrobenzyltosylates is, however, associated with certain disadvantages
which drastically limit the possibilities for use of the substances in
various fields of application. These disadvantages are described in detail
in DE 39 30 086.
Preferred photolytic acid-forming agents are, therefore, compounds that
form strong acids and that do not have a corrosive action, e.g., sulfonic
acids. Preferred acid-forming agents of this type are, for example,
bis(sulfonyl)diazomethanes (DE 39 30 086), sulfonylcarbonyldiazomethanes
(DE 39 30 087) and o-diazonaphthoquinone-4-sulfonates.
Bis(sulfonyl)diazomethanes are particularly preferred.
The content of photoactive acid-forming agents in the mixture according to
the invention is generally between about 0.5 and 25% by weight, preferably
between about 1 and 10% by weight and particularly preferably between
about 2 and 7% by weight, in each case based on the total weight of the
layer.
Upon exposure of the mixture according to the invention to actinic
radiation a strong acid is formed by photolysis of the photoactive
acid-forming agent, which acid splits the C--O--C or C--O--Si bonds in the
acid-labile compounds. As a result, the exposed regions of the
photosensitive layers become soluble in an aqueous-alkaline developer.
This effect is intensified by the conversion of the diazoketo function in
the side chain of the radiation-sensitive polymer units of the binder into
a carboxylic acid function.
The radiation-sensitive mixture according to the invention is distinguished
by a good differentiation between exposed and unexposed regions of the
layer and by a high photosensitivity over a broad spectral range. It has a
high thermal stability and provides detail-accurate reproduction even of
extremely fine structures in an original. Preferably, no corrosive
photolysis products are liberated as a result of the exposure, so that the
mixture can also be used on sensitive substrates.
The radiation-sensitive binders according to the invention which contain
groups of the general formula II and have been characterized in more
detail above are outstandingly suitable as radiation-sensitive polymers in
a radiation-sensitive mixture for the production of high-resolution
photoresists for microlithography. The compounds according to the
invention are particularly suitable for exposure to actinic radiation. In
this context, actinic radiation should be understood to be any radiation
whose energy corresponds at least to that of short-wave visible light. UV
radiation is suitable, in the range from about 190 to 450 nm, preferably
from about 200 to 400 nm and particularly preferably from 200 to 300 nm.
Electron radiation and X-rays are also suitable.
The present invention also relates to a process for the preparation of the
polymers according to the invention containing side groups of the general
formula II. In this process it has proved particularly advantageous first
to prepare suitable precursors, which contain groups of the general
formula III, and then to convert these groups into the groups of the
formula II in a subsequent reaction by means of a so-called diazo transfer
(cf. M. Regitz et al., Org. Prep. Proceed. 99 (1969)).
To this end, a polymer containing groups of the general formula III (in
which R has the meaning indicated in formula II)
##STR6##
is dissolved in a 5-fold to 50-fold, preferably 10-fold to 20-fold, amount
(based on the weight) of a suitable solvent and the solution is cooled to
a temperature between -15.degree. C. and +15.degree. C., preferably
-5.degree. C. and +5.degree. C. Suitable solvents are alcohols, such as
methanol and ethanol, hydroxyethers, such as ethylene glycol monomethyl
ether, chlorinated hydrocarbons, such as dichloromethane and
trichloromethane, aliphatic nitriles, such as acetonitrile, or mixtures of
these solvents. Preferred solvents are those which have a boiling point
between about 30.degree. C. and 140.degree. C. The reaction with the diazo
transfer reagent is appropriately carried out according to one of three
variants. These variants are, inter alia, described in detail in EP
378,068, and for this reason are not described here. Diazo transfer
reagents which have proved particularly suitable are aromatic and
aliphatic sulfonyl azides, such as p-toluenesulfonyl azide,
4-carboxybenzenesulfonyl azide, 2-naphthalenesulfonyl azide or methane
sulfonyl azide. The radiation-sensitive polymers prepared in this way can
be purified by known methods, for example, by means of crystallization or
chromatography (preparative GPC).
The preparation of the polymers containing side-chain .beta.-ketoester
groups, which serve as precursor, can, in turn, be carried out by various
procedures which are known in principle from the literature. A
particularly elegant procedure is the reaction of
5-acyl-2,2-dimethyl-[1,3]dioxane-4,6-dione (5-acyl-Meldrum's acid of
formula IV in which the radical R has the same meaning as in formula II)
##STR7##
with the polymer binder which contains groups of the general formula I.
The preparation of 5-acyl-Meldrum's acids and their reaction with
carbinols to form .beta.-ketoesters is known. The preparation can, for
example, be carried out analogously to the methods of Y. Oikawa et al., J.
Org. Chem. 43:2087 (1987) by reaction of acid chlorides with Meldrum's
acid, or analogously to the method of P. Houghton and D. J. Lapham,
Synthesis 451 (1982).
The reaction is obtained by adding the amount of 5-acyl-Meldrum's acid
required to obtain the desired degree of conversion to the polymer binder
which contains phenolic hydroxyl groups and then dissolving the mixture in
the 5-fold to 20-fold, preferably approximately 10-fold, amount of a
solvent which does not react with alcohols or with the 5-acyl-Meldrum's
acid. For example, a ketone, such as acetone or ethyl methyl ketone, or an
ether, such as 1,2-dimethoxyethane or dioxane, can be used, if appropriate
with heating. The clear solution is then heated to a temperature of
60.degree. C. to 120.degree. C., preferably 80.degree. C. to 100.degree.
C. The start of the reaction is discernable by vigorous evolution of
carbon dioxide. The mixture is stirred at the above-mentioned temperature
for about 1 to 6 hours, preferably about 2 to 4 hours, until no further
evolution of CO.sub.2 can be observed.
The solvent is then stripped off under vacuum, the reaction mixture as a
rule foaming vigorously. The product is obtained in high purity, so that
as a rule it is possible to dispense with a further purification in
accordance with the known methods.
The preparation of the polymers containing side-chain .beta.-ketoester
groups used as precursor can also be carried out by reaction of polymers
which contain groups of the general formula I with .beta.-ketoesters of
the general formula V
R--CO--CH.sub.2 --CO--OR" (V)
in which R" is in particular methyl or ethyl. The transesterification
reaction for the preparation of monofunctional .beta.-ketoesters has been
described, for example, by A. R. Bader et al. in J. Amer. Chem. Soc.
73:4195 (1951).
If the polymers containing side-chain .beta.-ketoester groups are to be
prepared by transesterification of compounds of the general formula V,
these compounds are generally used in an excess of up to about 20%,
preferably in an excess of about 5 to 10%, over the amount theoretically
required to achieve the desired degree of conversion. The
transesterification takes place in general at about 80.degree. to
160.degree. C. preferably at about 100.degree. to 140.degree. C. If
necessary, a solubilizing agent, such as dimethylformamide or
N-methylpyrrolidone, can be added in order to increase the solubility of
the hydroxyl group containing polymer in the .beta.-ketoester of the
general formula V. The reaction equilibrium is shifted in the desired
direction by distilling off the lower alcohol formed under a pressure of
about 800 to 20 mm Hg, preferably under a pressure of about 400 to 100 mm
Hg. When the amount of lower alcohol theoretically expected has been
distilled off, the excess .beta.-ketoester of the general formula V and,
where appropriate, the added solubilizing agent, are distilled off under a
high vacuum. The residue is frequently obtained in the form of a
voluminous, solidified foam. It consists of polymers containing side-chain
.beta.-groups in high purity, so that these can be used without further
purification in the diazo transfer reaction.
The .beta.-ketoesters of the general formula V required for this reaction
sequence are commercially available in some cases or can be prepared by
methods known from the literature. Their preparation from the
corresponding 5-acyl-Meldrum's acids of the general formula IV is
particularly preferred. Although this procedure requires an additional
reaction step compared with the process variant first described, improved
yields and/or purer polymers containing side-chain .beta.-ketoester groups
can be obtained in some cases using this variant. The preparation of the
polymers containing side-chain .beta.-ketoester groups by reaction of
.beta.-ketoesters of the general formula V with hydroxyl group-containing
polymers is, however, not preferred.
Both variants are described in detail in EP 378,068 and in the literature
references cited above and are therefore not further described here.
In addition, dyes, pigments, plasticizers, wetting agents, levelling
agents, and also polyglycols and cellulose ethers, for example,
ethylcellulose, can optionally be added to the radiation-sensitive
mixtures according to the invention in order to meet specific
requirements, such as flexibility, adhesion and gloss.
Preferably, the radiation-sensitive mixture according to the invention is
dissolved in a solvent or in a combination of solvents. Solvents
particularly suitable for this purpose are ethylene glycol and propylene
glycol as well as the monoalkyl and dialkyl ethers derived therefrom, in
particular the monomethyl and dimethyl ethers and also the monoethyl and
diethyl ethers, esters derived from aliphatic (C.sub.1 -C.sub.6)carboxylic
acids and either (C.sub.1 -C.sub.8)alkanols or (C.sub.1
-C.sub.8)alkanediols or (C.sub.1 -C.sub.6)alkoxy-(C.sub.1
-C.sub.8)alkanols, for example, ethyl acetate, hydroxyethyl acetate,
alkoxyethyl acetate, n-butyl acetate, propylene glycol monoalkyl ether
acetate, in particular propylene glycol methyl ether acetate, amyl
acetate, ethers, such as tetrahydrofuran and dioxane, ketones, such as
methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone and
cyclohexanone, N,N-dialkyl-carboxylic acid amides, such as
N,N-dimethylformamide and N,N-dimethylacetamide, and also
hexamethylphosphonic acid triamide, N-methylpyrrolidin-2-one and
butyrolactone, as well as any desired mixtures thereof. Among these
solvents, the glycol ethers, aliphatic esters and ketones are particularly
preferred.
Ultimately the choice of the solvent or solvent mixture depends on the
coating method used, the desired layer thickness and the drying
conditions. In addition, the solvents must be chemically inert towards the
other layer constituents under the conditions employed.
The mixture dissolved in the solvents generally has a solids content of
about 5 to 60% by weight, preferably up to about 50% by weight. The
invention also relates to a radiation-sensitive recording material which
is essentially composed of a substrate and a radiation-sensitive mixture
applied thereto.
Suitable substrates are all materials from which capacitors,
semiconductors, multilayer printed circuits or integrated circuits can be
composed or produced. Silicon substrates, which can be oxidized by the
action of heat, coated with aluminum, or doped, should be mentioned in
particular. In addition, all other substrates customary in semiconductor
technology are possible, such as silicon nitride, gallium arsenide and
indium phosphide. Further suitable substrates are the substrates known
from the production of liquid crystal displays, such as, for example,
glass and indium-tin oxide, and also metal plates and foils, for example
made of aluminum, copper or zinc, bimetal and trimetal foils, also
electrically non-conducting films on which metals have been
vapor-deposited, and paper. These substrates can be subjected to a heat
pretreatment, surface-roughened, slightly etched or, in order to improve
desired characteristics, for example, in order to increase the
hydrophillic character, pretreated with chemicals.
In order to provide the radiation-sensitive layer with a better cohesion
and/or a better adhesion to the substrate surface, this layer can contain
an adhesion promoter. In the case of silicon or silicon dioxide
substrates, suitable adhesion promoters are those of the aminosilane type,
such as 3-aminopropyltriethoxysilane or hexamethyldisilazane.
Suitable supports for the production of photomechanical recording layers,
such as printing forms for letterpress printing, planographic printing,
screen printing and flexographic printing are, in particular, aluminum
plates, which optionally have been anodically oxidized, granulated and/or
silicate-treated beforehand. Zinc and steel plates, which optionally have
been chromium-plated, can also be used, as well as plastic films and
paper.
The recording material according to the invention is exposed imagewise
using actinic radiation. Suitable radiation sources are, in particular,
metal halide lamps, carbon arc lamps, xenon lamps and mercury vapor lamps.
Exposure can also be carried out using high-energy radiation, such as
laser or electron radiation or X-rays. However, lamps which are able to
emit light having a wavelength of about 190 to 260 nm, i.e., in particular
xenon lamps and mercury vapor lamps, are particularly preferred. In
addition, laser light sources can also be used, for example Excimer
lasers, in particular KrF or ArF lasers, which emit at 248 and 193 nm,
respectively. The radiation sources must have an adequate emission in the
specified wavelength ranges.
The thickness of the light-sensitive layer depends on the intended use. It
is generally between about 0.1 and 100 .mu.m, preferably between about 0.5
and 10 .mu.m and particularly preferably about 1.0 .mu.m.
The invention also relates to a process for the production of a
radiation-sensitive recording material. The radiation-sensitive mixture
can be applied to the substrate by spraying on, flow-coating, rolling,
whirler-coating and dip-coating. The solvent is then removed by
evaporation, so that the radiation-sensitive layer remains behind on the
surface of the substrate. The removal of the solvent can be promoted by
heating the layer to a temperature of up to about 150.degree. C. However,
the mixture can also first be applied in the above-mentioned manner to a
temporary support, from which it is transferred to the final support
material under pressure and at elevated temperature. In principle, all
materials which are suitable as support materials can be used as temporary
support. The layer is then irradiated imagewise and treated with a
developer solution, which dissolves and removes the irradiated regions of
the layer, so that an image of the original used for the imagewise
exposure remains behind on the substrate surface.
Suitable developers are, in particular, aqueous solutions which contain
silicates, metasilicates, hydroxides, hydrogen phosphates and dihydrogen
phosphates, carbonates and hydrogen carbonates of alkali metal, alkaline
earth metal and/or ammonium ions, and also ammonia and the like.
Developers free from metal ions are described in U.S. Pat. No. 4,729,941,
EP 62,733, U.S. Pat. No. 4,628,023, U.S. Pat. No. 4,141,733, EP 97,282 and
EP 23,758. The content of these substances in the developer solution is
generally about 0.1 to 15% by weight, preferably about 0.5 to 5% by
weight, based on the weight of the developer solution. Developers free
from metal ions are preferably used. If appropriate, small amounts of a
wetting agent can be added to the developers, in order to facilitate the
removal of the exposed areas in the developer.
The developed layer structures can be post-cured. This is generally
effected by heating on a hot plate up to a temperature below the flow
point and subsequently exposing the entire surface to UV light from a
xenon/mercury vapor lamp (range from 200 to 250 nm). As a result of the
post-curing, the image structures are crosslinked, so that they generally
exhibit flow resistance up to temperatures in excess of about 200.degree.
C. The post-curing can also be effected without a rise in temperature,
solely by irradiation with high-energy UV light.
The compounds according to the invention are used in radiation-sensitive
mixtures for the production of integrated circuits or of discrete
electrical components in lithographic processes, since they have a high
photosensitivity, especially upon irradiation with light of a wavelength
of between about 190 and 300 nm. Since the mixtures bleach very well on
exposure, imaging can be achieved which is distinctly superior to that of
the known mixtures with respect to resolution. The recording material
produced from the mixture serves as a mask for the subsequent process
steps. These include, for example, milling of the layer support,
implantation of ions in the layer support or the deposition of metals or
other materials on the layer support.
The following examples are intended to illustrate the preparation of the
radiation-sensitive polymers according to the invention and their use.
However, they are not intended to restrict the invention in any way.
PREPARATION EXAMPLES
Example 1
Linking of 2-diazo-1,3-dicarbonyl side chains to poly
(3-methyl-4-hydroxystyrene)
Step 1:
An amount of 3.01 g (11.8 mmol) of
5-(cyclohexylhydroxymethylene)-2,2-dimethyl-[1,3]dioxane-4,6-dione and
8.00 g of a homopolymer of 3-methyl-4-hydroxystyrene having an average
molecular weight of 30,000 and a hydroxyl number of 390 are dissolved in
50 ml of acetone and warmed slowly. Above about 60.degree. C. a vigorous
evolution of carbon dioxide starts. The solution is then refluxed for an
additional hour. The solvent is distilled off in the course of two hours
under normal pressure and at a bath temperature of 100.degree. C. Solvent
residues and other readily volatile constituents are removed under a high
vacuum. During this operation the reaction mixture foams vigorously. After
cooling the reaction mixture, a solidified, slightly yellowish and
voluminous polymer containing .beta.-ketoester groups is obtained which
can be used without further purification as the starting material for the
next step.
Step 2:
The polymer obtained in step 1 is dissolved in 200 ml of acetonitrile and
the solution is then cooled to 0.degree. C. An amount of 2.33 g (11.8
mmol) of p-toluenesulfonic acid azide are added to the cooled solution,
with stirring, and 1.26 g (12.4 mmol) of triethylamine are then added
dropwise at a rate such that the temperature does not rise above 5.degree.
C. After stirring for five hours, no further p-toluenesulfonyl azide is
detectable in the mixture by thin layer chromatography (silica gel,
eluent: ethyl acetate). The solvent is then distilled off under vacuum and
the residue is taken up in 100 ml of ethyl acetate. The solution is added
dropwise to hexane, whereupon a precipitate forms which is filtered off
and dried under vacuum. An amount of 9.9 g (98% ) of a slightly yellowish
polymer, (containing polymer units of the general formula II), which has a
hydroxyl number of 235, are obtained.
IR (KBr): 2.136 cm.sup.-1 (C=N.sub.2)
If appropriate, the product is recrystallized from solvent mixtures
composed of ethanol, ethyl acetate, tetrahydrofuran and hexane. In a few
cases preparative GPC was used for further purification.
Other polymers which contain side-chain 2-diazo-1,3-dicarbonyl groups can
be prepared in an analogous manner. A few selected examples are listed in
the table below. The radiation-sensitive polymers according to the
invention were characterized by determination of the hydroxyl number, by
.sup.1 H and .sup.13 C high-field nuclear magnetic resonance spectra, and
by IR spectra (C=N.sub.2 oscillation) and elementary analyses. All
experimental values agreed well with the values to be expected
theoretically. The yields were good to very good in all cases.
EXAMPLES 2 TO 37
______________________________________
Polymer Diazo
Monomer Type content
No. a) Ratio b) R c) [%]
______________________________________
2 a 100 H cyclohexyl
10
3 a 100 H 2-phenylethyl
15
4 a 100 H n-butyl 15
5 a:b 75:25 B cyclohexyl
20
6 a:b 75:25 C cyclohexyl
20
7 a:b 65:35 C ethyl 40
8 a:j 75:25 C cyclohexyl
15
9 a:k 90:10 B methyl 20
10 a:k 90:10 B phenoxymethyl
15
11 b 100 H cyclohexyl
70
12 b 100 H cyclohexyl
85
13 b:c 50:50 C cyclohexyl
15
14 b:c 60:40 C cyclohexyl
50
15 b:d 20:80 C methyl 60
16 b:d 35:65 C 3-methoxy-
35
carbonylpropyl
17 b:e 50:50 C cyclobutyl
35
18 b:k 15:85 B cyclohexyl
65
19 b:l:o 30:20:50 T benzyl 40
20 b:m:o 25:25:50 T benzyl 30
21 b:n:p 20:30:50 T 2-phenylethyl
20
22 c:k 80:20 B tert.-butyl
10
23 d:r 70:30 C n-octyl 40
24 d:s 30:70 C 2-methoxy-
10
carbonylethyl
25 d:t 50:50 C 2,5-dioxahexyl
40
26 f 100 H cyclohexyl
15
27 g 100 H cyclohexyl
35
28 h 100 H methyl 10
29 i 100 H methyl 5
30 q 100 H cyclohexyl
5
31 r 100 H cyclohexyl
60
32 s 100 H cyclohexyl
15
33 s:o 50:50 C i-butyl 20
34 t 100 H cyclohexyl
20
35 t:p 30:70 C n-hexyl 5
36 u 100 H cyclohexyl
10
37 u 100 H i-propyl 10
______________________________________
(a) Monomer constituents (k=polymer): a=4-hydroxy-3-methylstyrene;
b=4-hydroxystyrene; c=4-hydroxy-3,5-dimethylstyrene; d=styrene;
e=3-ethyl-4-hydroxystyrene; f=4-hydroxy-3-methoxystyrene;
g=3-hydroxystyrene; h=4-hydroxy-3-propylstyrene;
i=3-butyl-4-hydroxystyrene; j=.alpha.-ethyl-4-hydroxystyrene; k=novolak
(resin S); 1=n-octyl vinyl ether; m=n-octadecyl vinyl ether;
n=trimethylvinylsilane; o=N-cyclohexylmaleimide; p=N-phenylmaleimide;
q=pyrocatechol monomethacrylate; r=resorcinol monomethacrylate;
s=pyrogallol monomethacrylate; t=phloroglucinol monomethacrylate;
u=3,4,5-monomethacrylate.
(b) Binder type: B=blend (mixture), C=copolymer, H=homopolymer,
T=terpolymer.
(c) Based on the phenolic hydroxyl groups converted in the binder
containing polymer units of the general formula I, on which the binder is
based (in the case of the binders containing two phenolic hydroxyl groups
per polymer unit (with the monomer constituents a, s, t and u), the
content relates to the average degree of conversion per hydroxyl group
present.
Examples 38 to 45 confirm the suitability of the mixture according to the
invention for recording materials in microlithography when using radiation
of different energies. The superiority of the mixtures according to the
invention over those known from the prior art is confirmed on the basis of
Comparison Examples 46 and 47.
USE EXAMPLES
The coating solutions were filtered through filters having a pore diameter
of 0.2 .mu.m and spin-coated onto a wafer pretreated with an adhesion
promoter (hexamethyldisilazane). The speed of rotation of the spin-coater
was chosen so that layer thicknesses of about 1.07 .mu.m were obtained
after drying at 90.degree. C. for 1 min on the hot plate.
The recording material was exposed imagewise under an original to the UV
radiation from a KrF Excimer laser (248 nm) or a xenon/mercury vapor lamp
(260 nm, with interference filter) and then subjected to a post-exposure
bake at 70.degree. C. for 1 min on a hot plate. The recording material was
developed using a 0.27N aqueous (tetramethyl)ammonium hydroxide solution.
In the following examples parts by weight are abbreviated to pwt.
EXAMPLE 38
A photosensitive recording material was prepared with a coating solution
composed of
______________________________________
5.625 pwt
of the radiation-sensitive polymer from Example 1,
1.875 pwt
of p-methoxybenzaldehyde bis(phenoxyethyl)acetal,
prepared analogously to Preparation Example 1 of
DE 37 30 787, and
0.35 pwt
of the 2,1-diazonaphthoquinone-4-sulfonic acid ester of
2-ethoxyethyl bis-4,4'-(4-hydroxyphenyl)-n-valerate,
and
42.5 pwt
of propylene glycol monomethyl ether acetate.
______________________________________
Developing time: 120 s;
Exposure dose: 48 mJ/cm.sup.2 (Excimer laser).
EXAMPLE 39
A photosensitive recording material was prepared with a coating solution
composed of
______________________________________
6.0 pwt of the radiation-sensitive polymer from Example 2,
1.5 pwt of 3,4-dimethoxybenzaldehyde-bis
(phenoxyethyl)acetal, prepared analogously to
Preparation Example 1 of DE 37 30 787,
0.5 pwt of bis(4-tert-butyl-benzenesulfonyl)-
diazomethane (see DE 39 30 086), and
42.5 pwt
of propylene glycol monomethyl ether acetate.
______________________________________
Developing time: 12 s
Exposure dose: 38 mJ/cm.sup.2 : (Excimer laser).
EXAMPLE 40
A wafer coated in accordance with Example 38 was irradiated under an
original with UV light from a xenon/mercury vapor lamp with an energy of
50 mJ/cm.sup.2.
Developing time: 120 s.
EXAMPLE 41
A photosensitive recording material was prepared with a coating solution
composed of
______________________________________
6.5 pwt
of the radiation-sensitive copolymer from Example 13,
3.5 pwt
of benzaldehyde bis(phenoxyethyl)acetal, prepared
analogously to Preparation
Example 1 of DE 37 30 787, and
1.0 pwt
of bis-(4-tert-butyl-benzenesulfonyl)-
diazomethane (DE 39 30 086), and
39.0 pwt
of propylene glycol monomethyl ether acetate.
______________________________________
Developing time: 60 s;
Exposure dose: 35 mJ/cm.sup.2 (Excimer laser).
EXAMPLE 42
A photosensitive recording material was prepared with a coating solution
composed of
______________________________________
7.5 pwt
of the radiation-sensitive terpolymer from Example 21,
2.5 pwt
of benzaldehyde bis(phenoxyethyl)acetal,
prepared analogously to Preparation
Example 1 of DE 37 30 787, and
0.6 pwt
of bis-(benzenesulfonyl)-diazomethane (see
DE 39 30 086), and
45.0 pwt
of propylene glycol monomethyl ether acetate.
______________________________________
Developing time: 100 s;
Exposure dose: 31 mJ/cm.sup.2 (xenon/mercury vapor lamp).
EXAMPLE 43
A photosensitive recording material was prepared with a coating solution
composed of
______________________________________
8.0 pwt of the radiation-sensitive homopolymer from
Example 30,
2.0 pwt of 3,4-(methylenedioxy)benzaldehyde
bis(phenoxyethyl)acetal,
0.3 pwt of the 7-methoxynaphthoquinone-2-diazide-
4-sulfonic acid ester of 2-ethoxethyl
4,4,-bis-(4-hydroxyphenyl)-n-valerate, and
40.0 pwt of propylene glycol monomethyl ether acetate.
______________________________________
Developing time: 90 s;
Exposure dose: 42 mJ/cm.sup.2 (xenon/mercury vapor lamp).
EXAMPLE 44
A photosensitive recording material was prepared analogously to Example 39,
but using 1.5 pwt of terephthalic dialdehyde tetrakis(phenoxyethyl)acetal
instead of 1.5 pwt of 3,4-dimethoxybenzaldehyde bis(phenoxyethyl)acetal as
the acid-labile component.
Developing time: 75 s;
Exposure dose: 36 mJ/cm.sup.2 (Excimer laser).
EXAMPLE 45
A photosensitive recording material was prepared with a coating solution
composed of
______________________________________
6.0 pwt
of the radiation-sensitive copolymer from Example 6,
2.3 pwt
of terephthalic dialdehyde tetrakis-
(phenoxyethyl)acetal,
0.55 pwt
of benzenesulfonyl-p-toluoyl-diazomethane
(see DE 39 30 086), and
42 pwt of propylene glycol monomethyl ether acetate.
______________________________________
Developing time: 85 s;
Exposure dose: 44 mJ/cm.sup.2 (Excimer laser).
Evaluation of the Developed Recording Materials
The resist structures obtained according to Examples 38 to 45 are a
defect-free image of the mask with steep resist edges. Structures less
than or equal to 0.50 .mu.m are reproduced in accurate detail. Examination
of the edges of the resist profiles using scanning electron microscopy
confirmed that these were aligned virtually vertically to the substrate
surface. The bleed into the unexposed resist regions was in all cases less
than 20 nm/min and the sensitivity of the resist formulation was in all
cases less than or equal to 50 mJ/cm.sup.2.
EXAMPLES 46 AND 47 (COMPARISON EXAMPLES).
The coating solution according to Example 38 was modified by replacing the
radiation-sensitive binder according to the invention used in that
example, with an equal amount of poly(3-methyl-4-hydroxystyrene) [M.sub.w
(GPC) 25,400] (Example 46) or poly(4-hydroxystyrene) [M.sub.w
(GPC)=20,400] (Example 47). Following exposure to radiation having a
wavelength of 248 nm and an energy of 38 or 36 mJ/cm.sup.2 respectively,
and developing, structures were obtained the resolution limit of which was
reached at about 1.0 .mu.m lines and spaces (Example 46) or which do not
exhibit image differentiation meeting the requirements in practice
(Example 47).
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